1. Technical Field
The present invention relates to light valve image projection systems, and more specifically, to multi-color light valve image projection systems.
2. Discussion
In conventional color projection systems employing optical light valves, three primary color images (red, green and blue) are displayed in optical registration on a viewing screen. The three primary color images are typically generated by three separate light valves and projected on the screen by three separate projection lenses. The projection lenses are arranged about an optical axis which typically passes through the composite image displayed on the screen. In such an arrangement, it is necessary that the three primary color images converge in the plane occupied by the screen. In other words, the convergence of the three primary color images is dependent upon the distance between the screen and the projection lenses. This method of projection suffers from the disadvantage that the projection lens arrangement must be reconfigured when the distance between the projection lenses and the screen is altered.
In certain applications the space which may be occupied by the projection system is limited. This often requires that the screen be positioned in relatively close proximity to the projection lens. Such a short "projection throw distance" generally necessitates usage of wide-angle projection lenses. However, the relatively large size of wide-angle lenses complicates the deployment thereof.
In other conventional color projection systems, a single projection lens having three sections is utilized in lieu of the set of three projection lenses. Again, however, the displacement of each lens section from a common optical axis precludes registration of the primary color images until convergence on the screen. As a consequence, systems incorporating sectioned projection lenses must also be altered in response to changes in the separation between the projection lens and screen.
Hence, a need exists for a compact, full-color optical light valve projection system in which convergence of the primary color images is relatively independent of the projection throw distance.